The Influence of Region-of-interest Selection on Ejection Fraction Calculation in a Septate Gallbladder

A 62-year-old woman with chronic nausea and epigastric pain underwent hepatobiliary scintigraphy. Gallbladder ejection fraction (GBEF) calculation suggested normal function. However, upon further review, a septate gallbladder was identified. This promoted a re-evaluation of the selected region of interest (ROI). The initial ROI included only the gallbladder fundus, leading to GBEF overestimation. Recalculation with a comprehensive ROI that encompassed both compartments yielded a lower GBEF, consistent with biliary dyskinesia or chronic cholecystitis. This case highlights the importance of ROI selection for accurate assessment of GBEF calculation in anatomical variations such as septate gallbladder and correlating functional studies with anatomical imaging.